Overvis MC261 Modbus Gateway with LoRa/Wi-Fi/Ethernet/RS-485 Operating Manual

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Overvis MC261 Modbus Gateway with LoRa/Wi-Fi/Ethernet/RS-485

This Operating Manual explains the design, safety requirements, operating rules, and maintenance procedures for the Overvis MC261 Modbus Gateway with LoRa/Wi-Fi/Ethernet/RS-485

Safety information

During operation and maintenance, observe the requirements of applicable regulatory documents, including:

Regulations for Operation of Consumer Electrical Installations;
Safety Rules for Operation of Consumer Electrical Installations;
Occupational Safety Rules for Operation of Electrical Installations.

Only qualified personnel who have studied this Operating Manual should perform installation, adjustment, and maintenance.

When used in accordance with this manual, the Overvis MC261 is safe in operation.

The Overvis MC261 meets the requirements of the following standards: EN 60947-1; EN 60947-6-2; EN 55011; EN 61000-4-2.

The device contains no hazardous substances in excess of maximum permissible limits.

The development and production quality management system complies with ISO 9001:2015.

General description

The Overvis MC261 is a programmable RS-485 / LoRa to Ethernet / Wi-Fi gateway and controller. It:

collects data from connected Modbus and LoraSens devices;
transfers data to a server or cloud service;
provides access to data via Modbus TCP or HTTP protocols;
tracks events and executes actions (for example, writing values to Modbus devices, or logging values to a memory card).

The Overvis MC261 provides the following capabilities:

Flexible connection options: 10/100 Ethernet (wired) or 2.4GHz Wi-Fi (wireless), automatic selection of the connection method to the cloud server, automatic or manual Wi-Fi addressing, automatic or manual Ethernet settings
Access security: no default password, passwords for Setup Mode and connections to the Modbus network, optional encrypted Wireguard VPN connection, connecting only to a selected cloud server
Flexible RS-485 communication: Modbus RTU or ASCII, even/odd/no parity, wide range of baud rates, adjustable delays
LoraSens wireless gateway: 868MHz Sensors (like temperature or weight) configuration and data collection
Programmable logic for data collection, event tracking, and actions in response to events (see Operations logic programming)
Service functions: real-time clock, astronomical timer, diagnostic logs, automatic or manual firmware update

Front panel and indicators

Technical drawing showing MC261 overall dimensions (64.5mm height, 90.2mm width, 36mm depth) and DIN-rail mounting specifications

Fig.1 – Overall and mounting dimensions of MC261

Front panel of MC261 showing LED indicators (PWR, LAN, WiFi, AL, SD, SRV, 485), LCD display, and service button R

Fig.2 – Controls of the Overvis MC261

PWR LED is on when there is supply voltage;
LAN LED is on when connected to Ethernet network, and is blinking during the data exchange on the network;
The display shows the state of the device, active connections, device addresses, and the load of communication interfaces;
WiFi LED flashes 3 times per second in Access Point mode, flashes every 3 s when searching; is continuously on when joined;
AL LED warns about the error as a result of analysis of the received data;
SD is on when there is a memory card in its slot, and is blinking during the data exchange with the memory card;
SRV is on when the connection is present with the cloud server (or VPN), and is blinking during the data exchange via this connection;
485 is on when waiting for data from a device on RS-485 bus, and is blinking during the data exchange on this bus;
R service button (accessible through a hole in the front panel, press with a thin non-conducting object) grants quick access to MC261 or resets the controller.

Operating conditions

The Overvis MC261 is designed for operation under the following environmental conditions:

Ambient temperature: –35 … +55 °С
Atmospheric pressure: 84 … 106.7 kPa
Relative humidity (at +25 °С): 30 … 80%

Delivery set

Table 1 – MC261 delivery set

Item	Quantity
MC261	1
Cable for Ethernet connection	1
LoRa antenna	1
Memory card (microSD 2 GB)	1
Operation Manual	1
Packing	1

Technical specifications

Table 2 – MC261 technical specifications

Parameter	Value
DC rated supply voltage	12 V
Data exchange interfaces via wired network	10Base-T/100Base-T Ethernet, RS-485
Supported Ethernet protocols	UDP, ARP, TCP, DHCP
Data exchange interface via wireless network	2.4 GHz IEEE 802.11 b/g/n
Supported standards of wireless network	UDP, TCP, DHCP
Integrated TCP/UDP clients	Modbus TCP, HTTP, WIREGUARD, NTP, DNS
Integrated TCP servers	Modbus TCP, HTTP
Maximum number of incoming TCP connections	4
Wireless sensor interface	LoRa, 868 MHz
Supported wireless sensor protocol	LoraSens
Maximum wireless sensors	40
Supported Modbus protocols via RS-485	Modbus RTU, Modbus ASCII
Transmission speed via RS-485	75 … 230400 bps
Maximal output voltage of driver RS-485	3.3 V
Short circuit output current of driver RS-485 (maximum)	250 mA
Resistance of built-in terminator	1000 Ohm
The recommended number of connected devices in RS-485 network:
– when the input current of receivers on RS-485 bus is less than 0.125 mA;	≤ 256
– when the input current of receivers on RS-485 bus is less than 1 mA	≤ 32
Readiness time when power is applied	≤ 4 s*
The supply voltage at which the operability is maintained	9 … 30 V
Power consumption (under load)	≤ 5 W
Device service	Switchgear and controlgear
Rated operating condition	Continuous
Protection class rating	IP20
Electric shock protection class	III
Climatic design version	NF 3.1
Overvoltage category	II
Rated voltage of insulation	450 V
Rated impulse withstand voltage	2.5 kV
Conductor cross-section for connecting to terminals	0.5 … 3 mm²
Tightening torque of the terminal screws	0.4 N·m
Weight	≤ 0.400 kg
Overall dimensions (Fig. 1), H×W×D	64.5 × 90.2 × 36 mm
Installation (mounting) of the device	On standard 35 mm DIN-rail
Device orientation	Operable in any position in space
Housing material	Self-extinguishing plastic

* Establishing connections in Ethernet / Wi-Fi / Internet/ VPN networks can take more time.

Device architecture

MC261 provides control over wireless LoraSens sensors and also Modbus devices in an RS-485 network, via Ethernet or Wi-Fi interfaces. It also supports reading LoraSens actual data, logs or Modbus devices data.

The processor supports connection to a cloud server:

via Ethernet network using an integrated Ethernet interface chip;
via Wi-Fi using a built-in module (used when Ethernet connection is not available).

In addition, MC261 can be connected via the Modbus TCP protocol to exchange data with Modbus devices or with another MC261 controller.

When you insert a memory card, MC261 loads the operation logic program into internal memory. This program defines data collection and event tracking. It runs in the background.

You can write collected data to the memory card in tabular or binary format. For registered events, you can configure actions such as writing corrected or converted Modbus values and commands.

MC261 stores network settings, security parameters, and operation logic in its built-in memory.

Installation and wiring

Before you start:

Unpack MC261 (we recommend keeping the original packing for the entire warranty period).
Check MC261 for damage after transportation. If you find any damage, contact the supplier or manufacturer.
Read this Operating Manual carefully (pay special attention to the power supply in the connection diagram).
If you have any questions regarding installation, contact the manufacturer.

Wiring requirements

If the temperature of MC261 after transportation or storage differs from the ambient operating temperature, keep MC261 under operating conditions for at least two hours before connecting it to the power supply. This prevents condensation on internal components.

To ensure reliable electrical connections, use flexible (stranded) wires. Strip the insulation from the wire ends by 5±0.5 mm and crimp with suitable ferrules. It is recommended to use wire with a cross-section of at least 1 mm².

When connecting to the RS-485 bus, use twisted-pair cable of category 1 or higher. A shielded cable is recommended; in that case, ground the shield according to “ANSI/TIA/EIA-485-A-1998”.
When connecting to Ethernet, use the supplied cable or a category 5e twisted-pair cable with an 8P8C (RJ-45) plug.

Route and fasten wires so as to avoid mechanical damage, twisting, or abrasion of the insulation.

For a reliable contact, tighten the terminal screws with the force indicated in Technical specifications.

To improve safety and reliability, it is recommended to install the fuse F1 (or its equivalent) in the MC261 supply circuit, rated for a current of no more than 2.5 A.

Electrical connection

Wiring diagram showing MC261 connections: power supply (9-30V DC) with fuse F1, RS-485 bus (contacts A and B), Ethernet LAN port, LoRa antenna

Fig.3 – Connection diagram of the device

F1 – fuse (fuse element) rated for 2.5 A;
Contact A – transmission of non-inverted signal;
Contact B – transmission of inverted signal.

Follow these steps to connect the MC261:

Connect the RS-485 bus cable to the RS-485 terminals (A and B) and to the RS-485 bus (or directly to the device with an RS-485 interface).
If the MC261 should connect to the Internet via wired communication, to a local network, or directly to a computer, connect the Ethernet cable to the LAN connector and to the Ethernet network (or directly to a computer). Connection details, depending on the network type, are provided in Connections.
Connect the appropriate DC power supply to the 9÷30V power connector.
Insert the memory card (microSD) into the MicroSD slot if you plan to use data logging or operation logic programming features.
Connect the LoRa antenna to the ANT connector (SMA F connector).

Power-up and normal operation

After power is turned on, all indicators except LAN light up, and MC261 performs initialization. After approximately 2 seconds, the indicators (except for the power indicator) go out, and the device proceeds to start the communication interfaces with networks. The display shows general information about the device (Fig. 4). Startup can take up to 15 seconds.

┌─────────────────────┐
│        MC261        │
│   © 2026 Overvis    │
│   FW Version 50     │
└─────────────────────┘

Fig.4 – Displaying of general information about the device on the display

After this, if enabled in settings, MC261 establishes a connection with the cloud server (or VPN) and starts executing the operation logic (if a program is loaded from the memory card). By default, cloud connections are disabled.

If configured, MC261 establishes TCP connections (via Ethernet and Wi-Fi networks) and waits for incoming TCP connections.

If Wi-Fi is configured and enabled, the WiFi indicator shows the wireless connection status: continuously on LED indicates successful network join (but no data transfer yet); non-periodic blinking indicates active data transfer.

The display shows the interfaces load, the Wi-Fi signal strength and the IP addresses used, as shown in Figure 5.

┌─────────────────────┐
│   E: 5.2к   S: 15%  │
│   (E) 10.0.0.2      │
│                     │
└─────────────────────┘
┌─────────────────────┐
│   W: 7-0.3к S: 15%  │
│   (W) 10.0.0.3      │
│                     │
└─────────────────────┘

Fig.5 – Displaying the status of connections on the display

E: 5.2k – the transmission speed via Ethernet is 5.2 kB/s;
W: 7-0.3k – the Wi-Fi signal level is 70 % and the transmission rate is 0.3 kB/s;
S: 15% – the load of RS-485 is 15 %.
(E): 10.0.0.2 – connection to the local network with the address 10.0.0.2;
(W): 10.0.0.3 – wireless connection with the address 10.0.0.3.

Communication modes

The Overvis MC261 is a protocol converter that bridges LoraSens and RS-485 Modbus RTU/ASCII networks with Modbus TCP networks. It operates in multiple communication modes simultaneously, providing flexible connectivity through Ethernet, Wi-Fi networks, and RS-485 interfaces. Each mode serves a distinct purpose and can be used independently or in combination to meet your application requirements.

LoraSens monitoring

MC261 can bind several LoraSens devices like temperature or weight sensors.

The controller collects and retains the devices data journals and actual data. The web interface and HTTP API support discovery, binding, device configuration, data reading, and journal operations.

RS-485 Modbus RTU/ASCII master mode

In master mode, MC261 forwards Modbus requests from TCP clients to devices on the RS-485 bus and returns their responses.

MC261 receives Modbus requests from TCP connections (incoming or outgoing)
Translates Modbus TCP requests to Modbus RTU/ASCII format
Forwards requests to target devices on the RS-485 network
Returns responses back to the TCP client
Supports both Modbus RTU and Modbus ASCII protocols

When an operation logic program is loaded, MC261 can also autonomously poll devices at configured intervals for data logging or event tracking purposes.

Request processing is described in detail in Modbus interface.

Use case: Data collection and event tracking for serial port equipment.

Integrated Modbus TCP server (slave mode)

MC261 acts as a Modbus TCP server, accepting incoming connections and processing Modbus requests.

Listens for incoming TCP connections from SCADA systems, HMI panels, or other Modbus TCP clients
Receives Modbus TCP requests from connected clients
Responds with its own register values or translates requests to Modbus RTU/ASCII and forwards them to RS-485 devices (in master mode)
Returns responses back to the TCP client
Supports up to 4 simultaneous incoming TCP connections
MC261’s own registers can also be accessed directly (current time, supply voltage, logic calculation results, etc.)

Use case: Access to the RS-485 serial port equipment for the TCP devices, HMI panels, SCADA and other Modbus TCP software.

Connection to remote Modbus TCP servers (master mode)

MC261 can establish outgoing connections to remote Modbus TCP servers, enabling it to forward requests to remote devices.

Initiates and maintains TCP connections to specified remote Modbus TCP servers via Ethernet, Wi-Fi or VPN
Forwards Modbus requests received from other sources (RS-485 master, incoming TCP connections, or operation logic) to these remote servers
Receives responses from remote servers and returns them to the requester
Can connect to multiple remote servers simultaneously (up to 3 connections can be configured)
Enables bridging between local RS-485 network and remote TCP-based Modbus devices

Use case: Data collection and event tracking for Modbus TCP equipment.

Reverse control translator mode (RS-485 slave, TCP master)

MC261 can operate as an RS-485 slave while acting as a Modbus TCP master, enabling reverse control scenarios.

Receives Modbus RTU/ASCII requests from an RS-485 master device
Translates these requests to Modbus TCP format
Forwards them to remote TCP servers or local TCP-based devices
Receives responses from TCP devices
Returns responses back to the RS-485 master in RTU/ASCII format

Use case: Access to the Modbus TCP equipment for the RS-485 serial port master device.

Tunnel mode (transparent data forwarding)

In tunnel mode, MC261 accepts data “as is” (without protocol verification) and forwards it to all other directions that are configured for this mode.

This allows transmission of data in formats different from the Modbus protocol. For example, arbitrary data received via RS-485 can be redirected to a remote TCP server, and vice versa.

Tunnel mode can be configured individually for:

Each connection to a remote TCP server
The RS-485 interface
Incoming connections to the Ethernet TCP port
Incoming connections to the Wi-Fi TCP port

First, a data packet from one direction is fully received (for Ethernet or Wi-Fi, this is one TCP packet; for RS-485, the packet length is determined by the Modbus RTU maximum-pause rules).

Then it is sequentially forwarded to the other tunnel directions (if there are more than two directions).

The maximum data packet length in tunnel mode is 254 bytes.

Use case: Connecting equipment with non-Modbus compatible protocols, or extending serial communication over IP networks.

Connection to cloud server (reverse connection) or VPN

MC261 can establish and maintain a persistent outbound connection to a cloud server (using Modbus TCP protocol or via VPN).

MC261 initiates the outbound connection to the server, bypassing firewall issues
In case of a Modbus protocol, after connection is established, MC261 sends its MAC address for identification as a first Modbus TCP packet (response for function 3)
After that it operates in slave mode, waiting for and processing server requests
The server sends Modbus requests through this connection
In case of an encrypted VPN connection, the server may also send HTTP requests
MC261 forwards these requests to RS-485 devices or responds with its own data
Returns responses back to the server
If the SRV LED is on, the connection to the server or VPN has been successfully established
If the SRV LED blinks, data is being exchanged via this connection

Use case: Centralized monitoring and control of distributed equipment through VPN or cloud platforms like Overvis Cloud, enabling remote access from anywhere without configuring firewall port forwarding or static IP addresses.

Network extension (long-range RS-485 bridging)

Pair two MC261 units to extend RS-485 networks beyond physical distance limitations by converting to/from TCP.

One MC261 operates in master mode on its RS-485 interface, while the other is in slave mode
First MC261 receives RS-485 signals and converts them to TCP packets
Data is transmitted over any distance via Wi-Fi or Ethernet networks
Second MC261 receives TCP packets and converts them back to RS-485 signals
Creates a transparent bridge between two RS-485 networks or segments
Works in both Modbus protocol mode (with address translation) and tunnel mode (fully transparent)
Each MC261 can operate in master or slave mode on its RS-485 interface as needed

Use case: Connecting RS-485 networks in separate buildings without running long cable runs, extending RS-485 beyond the 1200m distance limit, or accessing remote sites via Internet.

Network consolidation (address space remapping)

Combine multiple separate Modbus networks into one unified network by remapping device address spaces.

Connect multiple isolated RS-485 networks, each with its own set of device addresses and/or baudrate and parity settings
Configure address mapping to avoid conflicts (e.g., map first network’s UIDs 1-10 to 1-10, second network’s UIDs 1-10 to 11-20)
Access all devices from a single TCP or RS-485 interface as if they were on one network
Can combine local RS-485 devices with remote TCP devices seamlessly

Use case: Integrating multiple legacy systems with overlapping device addresses into a single SCADA system without physically re-addressing devices.

Data collection and event tracking

When an operation logic program is loaded into internal memory, MC261 reads specified parameters at a configured rate. These parameters may include registers of connected Modbus devices, MC261’s own registers, or MC261 memory.

The device then performs configured calculations and evaluates the received data. As a result, the following actions can be executed:

writing the read values to a log on the memory card;
writing new values to parameters (including values conversion, commands to other devices, etc.)

The program is loaded into internal memory from the memory card. The procedure for preparing and loading the program into the device is described in Operations logic programming.

Use case: Autonomous data logging to memory card for later analysis, or automated responses like regulation commands when scheduled time comes or temperature exceeds thresholds.

Configuration

MC261 configuration can be performed in two ways:

via the web interface using a browser (see Web interfaces);
via the Modbus protocol using any Modbus client software that works with MC261’s own registers (see Modbus interface).

Use the R button to grant quick access to MC261, toggle the Wi-Fi access point mode, restart the controller, or reset factory settings. Access the button through a hole on the front panel and press with a thin non-conductive object.

To reset the device to factory settings and clear the internal operation logic memory:

Press and hold the service button R for at least 11 seconds. After 2 seconds, the AL indicator will light up. After 11 seconds, the settings are reset, internal memory is cleared, and the device restarts; the indicators blink once.
Release the R button.

To toggle the Wi-Fi access point mode on and off:

Press and hold the service button R for 6 to 11 seconds. After 2 seconds, the AL indicator will light up.
When the AL indicator starts to blink, and the display prompts AP mode toggle on button release, then release the button. The device restarts; the indicators blink once.

To safely remove the memory card and restart the device (while preserving user settings):

Press and hold the service button R for 2 to 6 seconds.
When the AL indicator lights up and the display prompts reset on button release, then release the R button. If needed, remove the memory card after the SD indicator turns off.

To wake up the display, show connection information, and grant quick access to the device:

Briefly press and release the service button R.
The display lights up and shows connection information. For several minutes, configuration access (without a password) is granted for incoming connections.

Maintenance

Only qualified personnel should perform maintenance.
Recommended maintenance interval is every six months.

Check the reliability of wire connections; if necessary, retighten terminals with the torque specified in Technical Specifications.
Visually inspect the housing. If you detect cracks or other damage, take MC261 out of service and send it for repair.
If necessary, wipe the front panel and housing with a soft cloth.

Service life and warranty

The service life of MC261 is 10 years. After the service life expires, contact the manufacturer.
Shelf life is 3 years.
The warranty period is 5 years from the date of sale. During the warranty period, in the event of failure, the manufacturer provides free repair.

The place of purchase or the manufacturer performs warranty service.
The manufacturer performs post-warranty service at current rates.
Before sending MC261 for repair, pack it in the original or other packaging that protects it from mechanical damage.

When returning MC261 for warranty or post-warranty service, please provide a detailed reason for the return in the claims data field.

Transportation and storage

You may transport and store MC261 in the original package at temperatures from minus 45 to +60 °C and relative humidity of no more than 80%. When transporting MC261, protect it against mechanical damage.